look at these black clouds--there ___ be a heavy rain

题目

look at these black clouds--there ___ be a heavy rain
a) is going to
b) will

答案

选a,有clouds,表示下雨这个事情正在going中了
表示将来的有is going to, is to , is about to, 和will 四个
如果这几个都是备选,一般不选will